The use of an endless track as a traction enhancer for wheeled vehicles is well known. Typically, such belts comprise a plurality of individual track sections that are linked together for pivotal movement with respect to adjacent track sections. These track belts have traditionally been used to obtain better overall traction for the vehicle generally and in wet and slippery conditions particularly. Examples of such prior art track belts are disclosed in U.S. Pat. No. 3,497,271 to Keller, U.S. Pat. No. 4,089,565 to Loegering, et al., and U.S. Pat. No. 4,099,794 to Hoffart. The Keller patent discloses and claims a double-pivot linkage between adjacent track sections, whereas the Hoffart and Loegering patents disclose single pivot linkages wherein adjacent track sections are linked to each other about a single pivot pin connection. Single pivot linkage mechanisms are often used where the tires of the vehicle are extremely rounded, where three or more wheels will have a flexible belt mounted to them, or where there is a long wheelbase between adjacent wheels. In those circumstances, the single pivot linkage mechanism, such as that shown in Loegering '565 and Hoffart '794 are usually more desirable because they rock and flex less than the known double pivot linkages; that is, they are more rigid than the double or dual pivot linkage and therefore prevent substantial side tilting of the track sections and, therefore, the vehicle tires are less likely to walk out of the track belt.
Generally, each of the track sections include a base pad structure having an elongated shape that engages the ground during operation of the vehicle. The base pad forms a cross bar that extends between a pair of opposed sidewalls, which in turn each extend upwardly from the base pad on opposite longitudinally spaced ends thereof. Adjacent track sections are linked together by a linkage mechanism. Usually, though not necessarily, the linkage mechanism includes the sidewalls having at least one clevis type structure that receives a link therebetween. In a double or dual pivot linkage such as that shown in the Keller '271 patent, the link extends between adjacent clevises of adjacent track sections. In the single pivot linkage, one end of the link is integral with the side wall of one of the track sections and extends into a pivotal engagement with the clevis of the adjacent track section. In both linkage mechanisms, the clevis and the link have aligned apertures that receive a fastener or pivot pin that forms therewith the pivotal link mechanism by which the adjacent track sections are connected. As noted, a double or dual pivot linkage mechanism includes a pair of clevis structures for each track section by which the track section is pivotally connected on both lateral sides to the adjacent track sections.
During operation of a vehicle utilizing such flexible belts, the vehicle tires are normally guided within the track sections by the side walls of the track section. The prior art track sections usually guide the tires by engaging the soft side wall of the tire. For example, both the Hoffart '794 and the Loegering '565 track sections each tend to guide the tire utilizing the tire side wall, resulting in side wall wear on the tire.
In addition, during normal operation, the vehicle will often experience forces directed sideways to the track belt, or along the longitudinal direction of extent of the individual track sections. When experiencing these side loading forces, the tires will tend to crawl upwardly along the sidewall of the track section. This side loading of the tires into the sidewall of the track section creates wear on the tire, in particular on the tire sidewall, which is usually thinner and softer than the tire tread and thus more susceptible to wear.
On uneven terrain, such as where rocks are encountered by one side of a track section, the track belt can experience significant rocking and flexing of the individual track sections relative to adjacent track sections or of an end of a single track section relative to the other end thereof. This rocking and flexing of the track sections also contributes to tire wear as well as significant wear on the linkage mechanism connecting adjacent track sections. In the single pivot linkage mechanism the pivot pin is forced to endure a significant weight transfer due to the rigidity of the linkage between adjacent track sections. That is, when an object is encountered by one side of the track section, the track section will tend to tilt. Since it is rigidly, and often integrally, attached at one end of the link, however, tilting of the track section is inhibited and the tilting load is transferred to the pin, which can cause significant, accelerated wear on the linkages of a single pivot linkage. The pin in effect acts as a saw, increasing the wear. Because the track sections of a double pivot linkage are pivotally attached at on both sides, the track section can pivot independently on one side of the pad with respect to the opposite side thereof, thereby lessening the load transfer to the pin, and thereby reducing the wear. As noted previously though, known double pivot linkages are relatively more flexible and therefore facilitate the tire wheels to walk out of the track belt.
It would be desirable to have an improved track belt formed of double pivot track sections that subjected both the tires and the linkage mechanism between adjacent track sections to reduced wear.